I AM GETTING READY TO FINISH UP A R/D LONGBOW.I SHOOT 3 UNDER AND HAVE IT AT EVEN TILLER.GETTING GOOD ARROW FLIGHT WITH 3/4" NOCK SET.MY QUESTION IS BY GOING TO A POSITIVE TILLER 1/8 TO 1/4 WILL THAT BRING THE NOCK SETTING DOWN FOR  LEVEL ARROW TRAVEL AND WOULD THERE BE ANY BENEFIT TO THIS.

I don't know that I'd change anything if your arrows are flying really good, but your thinking is backwards... if you want to shoot from lower on the string, you need to further weaken the bottom limb, not the top.

One benefit of shooting the arrow closer to perpendicular is slightly better arrow flight due to faster recovery off the bow.